Non-elastomeric thermoplastic materials have been developed for use in a wide variety of applications. Non-elastomeric thermoplastic materials include many high polymers, usually synthetic, that are substantially solid, with little or no cold flow and plasticity, and can be formed or molded under heat and pressure and, sometimes, machined to high dimensional accuracy. Such non-elastomeric thermoplastic materials include those frequently referred to by the term "plastics" including, for example, polystyrene, polyurethane, polyethylene, polypropylene, acrylonitrile-butadiene-styrene, polyvinyl chloride, nylons, cellulosic resins, acrylic resins and the like. However, the mechanical properties of each individual non-elastomeric thermoplastic material, frequently limits the applications appropriate to that thermoplastic material. For instance, polyethylene is a generally inexpensive and non-elastomeric material with generally acceptable mechanical properties at very low temperatures and reasonable heat resistance. However, polyethylene has a low melting point and is not generally satisfactory for use in high temperature applications. Polystyrene is a generally non-elastomeric thermoplastic material that is generally not resistant to outdoor weathering, but has good optical qualities and has chemical resistance to most household acids. Other non-elastomeric thermoplastic materials generally have some advantageous properties, but also have disadvantageous properties, and many non-elastomeric thermoplastic materials have low resistance to impact, particularly at low temperatures.
Compositions, called modifiers, have been added to non-elastomeric thermoplastic materials to modify or enhance the mechanical properties such as abrasion resistance, solvent resistance, useful life, strength, and the like. Conventional modifiers typically include ethylene-propylene rubber (EPR), ethylene-propylene diene monomer (EPDM), nitrile-butadiene rubber (NBR), natural rubber (NR), ethylene-vinyl acetate copolymer (EVA), thermoplastic polyolefin rubber (TPO), as well as various other elastomers.
In the past, such modifiers have achieved only limited success, particularly in improving flame retardancy, hot and cold flow, chemical inertness, impact resistance, and resistance to ozone (O.sub.3)and ultraviolet light (UV). In addition, such conventional modifiers are typically blended with the thermoplastic in relatively high concentrations, that is, more than 10 percent by volume. These high concentrations of modifier increase the cost of the modified thermoplastic material and, therefore, a finished product. Moreover, even with the use of high concentrations of such modifiers, manufacturers of the modified thermoplastic compounds are limited to less than 5 percent fillers and extenders, such as reground tires, which can reduce the cost of the finished product.
The present invention provides improved non-elastomeric thermoplastic materials of the type generally referred to with the term "Plastics". Where, in this application, I refer to "non-elastomeric thermoplastic materials", or "non-elastomeric thermoplastics", I mean high polymer plastics, usually synthetic, that are substantially solid, with minimal plasticity and cold flow at normal atmospheric temperatures, and can be formed or molded with heat and pressure and, in some high polymer plastics, machined to high dimensional accuracy, including such high polymer plastics as polystyrene, polyurethane, polypropylene, polyethylene, acrylonitrile-butadiene-styrene, polyvinyl chloride, nylons, cellulose resins, acrylic resins and the like. Such improved non-elastomeric thermoplastics are modified with a modifier comprising an elastomer composition, polytetrafluoroethylene (PTFE), and molybdenum disulfide (MoS.sub.2), and can provide greatly improved physical properties, such as impact resistance, flame retardancy, flow characteristics, chemical inertness, and improved weatherability (such as resistance to O.sub.3 and UV), and can achieve such improvements at lower percentages of modifier, while permitting the non-elastomeric thermoplastic material to be loaded with increased percentages of fillers and extenders.